Timer for model airplanes



J1me 1953 H. F. AULER ET AL 2,640,295

TIMER FOR MODEL. AIRPLANES 3 Sheets-Sheet 1 Filed June 50, 1947 WWW/u 1% A 07 b E June 2, 1953 H. F. AULER ET AL 2,640,295

TIMER FOR MODEL AIRPLANES Filed June 30, 1947 S'Sheets-Sheet 2 Inventors /7,4Ro/ 0 [Al/15R Ewe/1' 0 ENE OP .5 w it nay June 1953 H. F. AULER ETAL [TIMER FOR MODEL AIRPLANES 5 Sheets-Sheet 5 Filed June 50, 1947 Invento rs Mmow 54% ER EQ/cH N:- Ko/as @w The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed in accordance with the best mode so far devised for the practical application of the principles thereof, and in which:

Figure l is a side view of a model airplane equipped with the timing device of this invention;

Figure 2 is a perspective view of that part of the timing device which is permanently attached to the model airplane;

Figure 3 is a perspective view of the removable part of the timing device, and which may be considered the timer proper;

Figure 4 is a longitudinal sectional view through the complete timing device with its switch open;

Figure 5 is a longitudinal sectional view through Figure 4 substantially on the plane of the line 5-5, but showing the piston latched in its cocked position at which the switch is closed to remain so until the piston returns to its position shown in Figure a;

Figure 6 is a cross sectional view on the plane of the line 6-5 in Figure i;

- Figure 7 is a cross sectional view through Figure l on the plane of the line 7-4;

- Figure 8 is a cross sectional view through Figure l on the plane of the line 8-8;

Figure 9 is a detail cross sectional view through Figure 4 on the plane of the line 9-4];

Figure 10 is a perspective View of some of the component parts of the timer unit illustrated in Figure 3, said parts being shown separated but in their proper order of assembly;

Figure 11 is an exploded perspective view'of the remainin parts of the timer unit;

Figure 12 is a perspective view of the piston and part of its stern; and

' Figure 13 is a fragmentary detail view looking down on the tail portion of the timer body.

Referring now more particularly to the accompanying drawings, in which like numerals indicate like parts throughout the several views, the numeral l designates a model airplane having a gas engine 2 mounted in the forepart of its fuselage 3 to drive a propeller 4. The engine has a spark plug 5 to which a lead 6 is attached. This lead is part of the ignition circuit of the engine. The ignition circuit is of conventional design and ineludes the usual components (not shown).

As pointed out hereinbeiore, gas engine powered model airplanes should be equipped with means for stopping the engine or motor after a short time, and for contest work this is a necessity since the regulations prescribe the maximum motor run. Opening the ignition circuit is the best way to stop the engine, and for this purpose a timer indicated generally by the numeral 1 is provided. While the use of timers to interrupt the ignition circuit is not broadly new, the timers heretofore employed for this purpose were not adapted to be mounted on the exterior of the model as shown in Figure 1. Hence, they lacked a very important feature of this invention for by mounting the timer on the exterior of the model, it is unrestrictedly accessible, making its adjustment and cocking a simple matter.

The specific shape and design of the timer 7 as well as its structural features (to be described) not only makes possible such external mounting but actually invites it and in addition enables the model builder to introduce desirable effects in the appearance of his model.

Structurally the timer 1 comprises two separable units 8 and 9. The unit 8 is essentially a plate of insulating material adapted to be permanently secured to the underside of the fuselage, as shown in Figure l, or to some other part of the model. Mounted on this plate are two electric terminals l0 and l i normally bridged by the engagement of spring contacts i0 and l I on the terminals. The terminals are secured to the top of the plate 8 at opposite sides of a rectangular hole l3, with their spring contacts Ill and ll extending towards each other from opposite ends of the hole to overlie and contact each other, and with the inner side edges of the terminals overhanging the sides of the hole, as best shown in Figure 8. Preferably, though not necessarily, the terminals [0 and H are recessed into the top of the plate.

Wire leads may be soldered to the terminals to permanently connect them in the ignition circuit; and as long as their spring contacts Hi and I l are engaged, the ignition circuit is closed, pro viding of course it is otherwise complete. The spring contacts thus provide a switch which, as will appear hereinafter, is closed when the two timer units 3 and 9 are detached from each other.

The unit '7 may be considered the timer per se. It comprises a streamlined or tear-drop shaped body l4 consistin of a nose I5, a mid section l6 and a tail section 11, all molded from an electrically insulating plastic. These three sections are cemented together in end-to-end relation during assembly.

Inside the body 14 is a cylinder 18, preferably a length of metal tubing, held in place by having its ends cemented into counterbores in the nose and tail sections. Within the cylinder is a piston i9 secured to the front end of a stem 20, and a spring 21 confined between the piston and a shoulder 22 on the tail section IT to yieldingly urge the piston towards the nose IS. A vent port 23 in the nose, adjusted by needle valve 24, provides means for regulating the rate of spring propelled forward movement of the piston [9. It is to be noted that the screw portion of the needle valve has an air escape slot 24 cut into the side thereof; and that the screw is readily accessible for adjustment even when the timer is in position on the model airplane.

The stem 20, like the body sections, is molded from plastic so as to be electrically non-conductive, and has a head 25 integral therewith. This head is of slightly smaller diameter than the bore of the cylinderand provides support for a leather cup 26 the bottom of which is clamped between the head 25 and a washer 21 slipped over the stem 20 and rotated to secure the same in position. For most of its length the stem has a non-circular cross section consisting of a round core 28 and diametrically opposite longitudinally extending ribs 29. Omission of the ribs 29 for a short distance directly adjacent to the head 25 provides shoulders by which the washer 21 is held against the leather cup upon rotation of the washer to disalign the opposite recesses of its non-circular hole from the ribs 29. The head 25, cup 25 and washer 21, of course, comprise the piston.

The rear end of the stem 20 slidably projects through an appropriately shaped hole in the end of the tail section I! to have a knob 30 cemented or otherwise secured thereto. By means of this knob, the piston is easily retracted to cock the timer. Such retraction of the piston effects closure of the timer controlled switch which comprises a pair of combined contact and terminal members 3|. These contact-terminal members are stamped from suitable metal and are held in place :by having narrow necks 32 "received in slots 13 formed in the tailsection .l'! and vclosedlziy a key 34 projecting from :the rear :endoi the mid section It. This key 31 serves the further purpose of holding the mid and tail sections in proper rotational relationship, necessitatedby the need for keeping bosses on these sections in line to conjointly forma pad '35. The'pad35 is'complementary to and merges with a pad 36 on the bottom of the plate 8 when the units 8 and 9 are connected.

The upper end portions of the members 3| project from the pad 35 and'are shaped to provide spring clips or connector terminals 3| adapted to enter the hole 13 -in the plate '8 and snap over the overhanging inner edges of the terminals I0 and H 'when-the'units '8 and 9 are connected. The detent action of these spring clips or connector terminals 3| snapping over the edges of the terminals Hi and H assures a good electrical connection and coacts with the engagement of a hook 31 over "the edge of a hole 38 in the plate 8 to removably hold the timer unit 9 attached to the plate unit 8. in attaching the timer unit, the hook'3l is first engaged over the edge of the hole 38 and then the rear end of the timer unit isswung up into place.

As the spring connector terminals 3| snap over the side edges of the terminals It and II thespring contact IO 'is "lifted out of engagement with the contact H by 2. lug 39 projecting up from the pad 35 betweenthe connector terminals 31 Thus, the timer switch is connected into the ignition circuit; and, as will be readily ap parent, when the timer unit '9 is removed, the contacts ll! and H i e-engage to close the ignition switch.

The timer switch actually comprises the inner end portions or the member 3| which straddle the stem 20 and are spring biased toward each other. The thickness of 'theportion of "the stem 20 between the members 3| at any given time determines whether the timer switch is open or closed.

For a distance slightly .less than the full stroke of the piston, the round core 28 of the stem is s'labbed on? at opposite sides, as at Ml, and the distance between the flat sides 40 is less than that required to hold the contact portions 31 of the members 3| separated. Thus, as long as the piston is in a positionat which the slabbedofi portion of thestem lies between the .members 3|, their contact portions 3H engage and the switch is closed, However, as the piston reaches the end of its forward spring propelled stroke, the inclined ends 4| of the slabbed-off stem portions move between the members 3| and spread them apart to disengage their contact portions.

The contact portionstl are preferably bifurcated with the extremity of one'legshaped to form a horizontal knife edge 42 and the extremity of the other leg shaped to form avertical .knife edge 43.

Inasmuch as the two members 3| are identical and oppose each "other, the knife edges 42 and 43 of opposite legs cross to provide single point contact therebetween. Hence, these switch contacts are less 'apttozb'e fouled by dirt or corrosion. The duplication of the contacts resulting from the bifurcation of the members rounded edge :to the stem 20 and thus minimize the frictional drag onthe stem.

During reciprocation of the stem and piston, the "stem is held against turning by its sliding engagement in the hole at the rear end of the tail section I1, "the inner portion M of which is of the same shape as the stem. However, when the'piston is fully retracted, .as in Figure 5, an interruption "45 in the ribs 29 aligns with the inner portion 4'4 of the hole in thetail section to allow rotation of the stem. The extent of this rotation is defined by the shape of the outer portion 46 of the hole in the "tail -piece,which -(as best shown in Figure 9) is angularly enlarged. Thus, when the stem is .pulled out to cook the timer, it may be turned a few degrees to engage the outer edges of the interruption 45 in the ribs 29 over the sides of the recesses in the hole portion '44. This latches the timer in its cocked condition.

Opening of the contacts 3| by the turning of the stem -to latch the timer in its cocked condition is precluded by having thezribs 2 9 relieved at 41, the relieved portions 41 being between the contacts 3| when the stem is fully pulled out.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention provides a timer for model airplanes which has many advantages over timers heretofore available for this purpose.

What we claim asour invention is:

l. A timer of the character described comprising: a body having complementary sections'joined together during assembly; a cylinder within the body secured therein upon juncture of the complementary sections of the body; a controllable air bleed leading from the cylinder; a piston operatingin the cylinder and biased in one direction; a stem on the piston projecting to the exterior of the body to provide means for moving the piston against its biasing force; switch terminals mountedin the body at the juncture of two of its complementary sections, said switch terminals having contact portions at opposite sides of the piston stem and relatively biased toward engagement with one another; and means on the piston stem operable upon said contact portions to control contacting engagement thereof during movement of said means with the piston.

2. In a time delay switch of the type comprisin adash pot and switch actuating means movable by the dash pot: a body composed of comple mentary sections molded from insulating material and adapted to accommodate a dash pot rnechanism; a switch actuating stem movable by the dash .pot across the plane of juncture between two complementary sections of thebody; a pair of elongated. sheet metal members of non-uniform cross section secured in correspondingly shape:- recesses in the body at thejuncture of said two complementary sections thereof, thenon-unifcrrn cross section of said members fitting in the cor respondingly shaped recesses to secure the inem- 'bers against displacement, at least one of said members having a part in juxtaposition to the switch actuating stem and. adapted to be actuated thereby; and complementary switch contacts on said members adaptedto be opened and closed in consequence to actuation of said one member by the stem.

3. A timing device for model airplanes, comprising: an elongated hollow body having a side wall; a time delay actuator in the body including an elongated stem constrained to endwise back and forth motion lengthwise of the body and spring propelled toward one limit of motion; control means carried by the body in its interior alongside of said stem to be operated thereby as the stem reaches its limit of spring propelled motion; connecting means on the side of the body at the exterior thereof for operatively connecting the timing device with a part of the model airplane to be controlled, said connecting means having operative connection with the stem operated control means and providing for maniiestation of the effect of operation thereof by the stem upon the part of the model airplane to be controlled; and means at said side of the body for attaching the body to the exterior of a model airplane to be controlled.

4. A timing device for model airplanes, comprising: an elongated hollow body having a side wall; a time delay actuator in the body including an elongated stem constrained to endwise back and forth motion lengthwise of the body and spring propelled toward one limit of motion; a switch carried by the side wall of the body and including a contactor inside the body movable crosswise or" the stem between switch closed and switch open positions and biased against the side of the stem and toward one of its two posit-ions; means on the side of the stem engageable with said contactor as the stem reaches its limit of spring propelled motion to move said contactor to its other position; a pair of terminals connected with said switch and projecting through the side wall of the body to the exterior thereof; and means at one side of the body for attaching the body to the exterior of a model airplane.

5. The combination of: a model airplane powered by an internal combustion engine having an ignition circuit; a combined mounting and terminal plate permanently fixed to the model airplane with one side of the plate accessible at the exterior of the airplane; spaced terminals on the plate permanently connected in the ignition circuit with the ignition circuit interrupted across the terminals so that closure of the ignition circuit requires the terminals to be electrically bridged; a switch on the plate for bridging said terminals; an enclosed timer unit having in its interior a switch actuator and time delay means for operating the same; means readily removably attaching the timer unit to said accessible side of the combined mounting and terminal plate; means on the timer unit independent of said attaching means for opening said switch in consequence to attachment of the timer unit to the r plate; and another switch carried by the timer unit having terminal portions exposed at the exterior of the timer unit for bridging the terminals on said plate when the timer unit is attached thereto, said other switch having movable contacts inside the timer unit and controlled by the switch actuator.

6. An electrical timins device for gas engine powered model airplanes and the like, comprising; a combined terminal and mounting plate adapted to be permanently secured to a model with one side of the plate exposed at the exterior of the model; terminals on said plate connectable in the ignition circuit of the engine of the model; switch means on said plate for electrically connecting said terminals with one another; an enclosed time delay switch unit including a movable actuator; cooperating means on said time delay switch unit and the plate for readily removably securing the time delay switch unit against said exposed side of the plate; and means on said time delay switch unit independent of said securing means but cooperable with said switch means for opening the same in consequence to attachment of said time delay switch unit to the plate; another switch inside the time delay switch unit controlled by the actuator thereof; and cooperating means on said plate and the time delay switch unit interengaged by attachment of the unit to the plate to electrically connect said last named switch with said terminals.

7. A motor run timer for model airplanes, comprising: a combined terminal and mounting plate adapted to be permanently attached to a model airplane with one side of the plate exposed at the exterior of the plane; terminals on said plate connectable in the ignition circuit of the motor in the model airplane; a hollow timer body; an adjustable dash pot type time delay switch actuating means within the body; switch means within the body controlled by said actuating means; and means detachably securing the timer body to said plate against the exposed side thereof, including spring clips on the body electrically connected with said switch means and extending through the side or" the body for interengagement with portions on said terminals to hold the body to the terminal plate and to electrically connect said time delay actuated switch means across said terminals.

8. In a timer for model airplanes: a terminal plate adapted to be mounted on a part of the model airplane with one side of the plate exposed at the exterior of the plane; terminals on said plate; an elongated timer housing having a side wall; dash pot type time delay switch actuating means within the housing; and means for detachably securing the housing to the terminal plate with a portion of the side wall of the housing against said exposed side of the terminal plate, including a pair of elongated flexible conductive strips extending through said portion of the side wall of the housing substantially parallel to one another, said strips having switch contacts at their inner ends controlled by said dash pot type actuating means and having means at their outer ends cooper-able with portions on said terminals on the terminal plate to hold the housing to the terminal plate and to electrically connect said contacts with the terminals.

HAROLD F'. AULER. ERICH EUGENE KO'HLS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,303,166 Colborn May 6, 1919 1,935,268 Ireland Nov. 14, 1933 2,035,648 Frank Mar. 31, 1936 2,207,189 Austin July 9, 1940 2,389,856 Jones Nov 27, 1945 FOREIGN PATENTS Number Country Date 477,305 Great Britain Mar. 20, 1936 

